This application is based on Application No. 24806 filed in Japan on Jan. 31, 2002, the content of which is incorporated hereinto by reference.
The present invention concerns a power source apparatus which is primarily installed in an electric powered automobile such as a hybrid car.
A power source apparatus, housing battery modules held in a case, is used for applications requiring large output such as electric motor powered automobiles. Battery modules are made up of rechargeable batteries connected in a straight line. As shown in FIG. 1, this type of power source apparatus contains battery modules 71 housed in a case 70. Battery modules 71 housed in the case 70 have output terminals 72 made up of bolts and nuts fixed at both ends. Output terminals 72 of the battery modules 71 are connected in series at bus-bars 73. End-plates 74 containing the bus-bars 73 are provided at side regions of the case 70. the end-plates 74 are formed of molded plastic with bus-bars inserted in the end-plates during molding for insulation. In this configuration of the power source apparatus, output terminals 72 of the battery modules 71 are connected to the bus-bars 73 by fastening battery module bolts 75 and nuts 76 to the end-plate 74 bus-bars 73.
In a power source apparatus with the configuration shown in FIG. 1, it is difficult to absorb length differences and attach battery modules to the case when the battery modules have different lengths. In particular, when battery modules disposed adjacent to each other have different lengths and are connected to a bus-bar, this configuration has the drawback that excessive tensile force is exerted on the shorter battery module and excessive compressive force is exerted on the longer battery module. Since battery modules have a plurality of rechargeable batteries connected in a straight line, there will be overall length variation when there is inaccuracy in rechargeable battery length. For example, if inaccuracy in the length of a nickel hydrogen battery used in a hybrid car is xc2x10.3 mm, a battery module made up of six of these rechargeable batteries connected in a straight line will have a maximum length error of xc2x11.8 mm. in this case, approximately 3 mm of length difference can develop between longest and shortest battery modules. Consequently, when battery modules of different lengths are disposed in adjacent, parallel positions and tightly connected with a bus-bar, considerable stress is exerted on long and short battery modules.
A configuration, which connects bus-bars to an end-plate while allowing some play, can absorb battery module length dimension error. However, this configuration has the drawback that the structure is complex and manufacturing cost is high. Further, if adjacent battery modules have different lengths, bus-bars cannot be connected without some force even when they are connected to end-plates with this configuration. This is because one bus-bar connected to battery modules with different lengths will have an inclined orientation connected to the output terminals.
As shown in FIG. 1, it is necessary to attach battery modules, made up of circular cylindrical batteries connected in a straight line fashion, to the case 70 in a manner that avoids battery module rotation. Output terminals 72 fixed to both ends of battery modules 71 in FIG. 1 have square and hexlgonical shapes to prevent battery module 71 rotation. Battery module 71 rotation is prevented by inserting these polygonal shaped output terminals 72 in the end-plates 74. Therefore, this power source apparatus has the drawback that a configuration which prevents battery module rotation is required, and end-plate and output terminal structure becomes complex.
Further, the power source apparatus shown in FIG. 1 has the drawback that the case itself has a complex structure. This is because of the requirement for end-plates formed by mold-insertion of the bus-bars. Since bus-bars cannot, be completely buried in the end-plates leaving bus-bar surfaces exposed, these regions must be further insulated by covering them with insulating plates. Further, since nuts and bolts are fixed to battery modules, the structure to attach output terminals to battery modules becomes complex. This is because nuts and bolts cannot be directly weld-attached to an end-plane of a battery in a battery module. It is necessary to first attach nuts and bolts to a metal plate by a method such as welding, then weld-attach the metal plate to a battery end-plane. This has the drawback that the structure is complex and assembly is time consuming.
Finally, a power source apparatus with the structure shown in FIG. 1 has the drawback that replacement of a specific battery module, when that battery module has failed, is extremely difficult. This is because it is necessary to remove the end-plates 74 to replace a battery module. To remove an end-plate 74, it is necessary to remove all nuts 76 and bolts 75 connected to battery modules 71. Since several tens of battery modules are housed in a case, it is extremely troublesome to remove all nuts and bolts and remove the end-plates.
The present invention was developed to correct these drawbacks. It is thus a primary object of the present invention to provide a power source apparatus with a simple structure allowing battery modules of different lengths to be joined without applying excessive force, allowing battery modules to be mounted in a case in a manner preventing their rotation without providing a special structure to prevent rotation, and also allowing extremely efficient and simple assembly and battery module replacement with a simple case structure.
The power source apparatus of the present invention has a plurality of battery modules housed in a case, and these battery modules are connected by bus-bars. Battery modules are made up of a plurality of batteries connected in a straight line fashion. Battery modules have metal plate output terminals attached at both ends to battery end-planes in a manner projecting outward from the end-planes. The power source apparatus has a case which houses battery modules with adjacent battery module output terminals connected via metal plate bus-bars.
The power source apparatus described above has the characteristic that battery modules of different lengths can be connected in a simple configuration without applying excessive force. This is because battery modules have metal plate output terminals attached at both ends perpendicular to, and projecting from battery end-planes, adjacent battery module output terminals are joined by metal plate bus-bars, and the assembly is housed in a case. In a power source apparatus of this configuration, output terminals attached to both ends of the battery modules face perpendicular to the axis of the battery module, not in the direction of the axis. For this reason even when battery modules of different lengths are disposed in a case in a parallel fashion and tightly connected via bus-bars, application of excessive force between battery modules can be reliably prevented while length differences are absorbed. Further, since the surface of metal plate output terminals projecting perpendicular from both ends of a battery module can support battery modules housed in the case, battery modules can be held in the case without rotation via a simple structure and without providing a special configuration to prevent battery module rotation.
Further, since the power source apparatus described above does not require molded end-plates with inserted bus-bars as in prior art, it has the characteristic that the structure of the case itself is simple and manufacturing cost can be reduced. Still further, the power source apparatus described above has the characteristic that a specific battery module can be easily and extremely efficiently replaced when it falls. This is because only the section of the case housing the battery module for replacement needs to be disassembled, not all the nuts and bolts and end-plate as in the prior art.
An output terminal preferably has a through-hole to accommodate a bus-bar attachment bolt. This through-hole can be a long narrow opening extending in the lengthwise direction of the battery module for the purpose of connecting to a bus-bar while absorbing battery module length variation.
The case can be provided with insertion sections to hold bus-bars and output terminals. The case can hold bus-bars and output terminals in the insertion sections and retain battery modules in fixed positions. The case insertion sections can be provided with enough tolerance to absorb errors in battery module length.
Nuts can be fixed to bus-bars. Bolts can be inserted through output terminal through-holes and screwed into nuts attached to the bus-bars to join output terminals and bus-bars in a more reliable fashion.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.